This application relates to a compact device for tapping the line power of a cable television distribution system.
Cable television distribution systems include line power on the cable used to distribute the RF TV signals. This power of about 60 volts quasi-square wave is used to power the line amplifiers which are dispersed throughout the system to amplify the TV signals. Generally the line power extends from the head end to the "taps" or boxes which connect one to ten subscribers to the cable line. Such taps are generally passive devices and do not utilize the power on the cable line, they merely remove it from the subscriber's "drop". The taps generally contain "ports" by which the distribution cable enters and exits. The ports are generally 5/8 inch threaded connectors but vary in depth from manufacturer to manufacturer.
Recently, interest has been generated in a new generation of "active" devices mounted at the tap box. Such devices can be scrambling/unscrambling devices or other means to prevent unauthorized cable service. Such devices, of course, require power and a clear choice for powering such device is the cable line power. However, various schemes for utilization of the cable power at the tap has frequently resulted in unacceptable interference and degradation of the RF signal. Degradation of the television signal may effect both the subscribers connected to the tap and those further down the distribution line. The utilization of the line power accordingly has generally been for temporary testing and servicing applications.
Compact line power tapping devices suitable for powering active devices have recently appeared. However, such devices are not sufficiently free of RF interference for many applications as such devices utilize relatively long rods to contact the hot side of the port. Such rods thus can contribute to degradation of the RF signal.